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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： M. Yi D. Lee A. Gola S. Merzi M. Penna J.S. Lee S. R. Cherry S.I. Kwon Department of Biomedical Engineering University of California Davis Davis California United States of America Interdisciplinary Program in Bioengineering College of Engineering Seoul National University Seoul Republic of Korea Fondazione Bruno Kessler Trento Italy Brightonix Imaging Inc Seoul Republic of Korea

ISBN: (数字)9798350388152

ISBN: (纸本)9798350388169

BGO has been highlighted as a cost-effective option for hybrid scintillator/Cherenkov radiator. However, effectively utilizing its improved timing resolution is hindered by challenges in managing the high detection fluctuation of Cherenkov photons and their spectral overlap with scintillation photons. Our previous study showed that the dual-ended readout and an adaptive timestamp method could enhance the detection of quasi-isotropically and simultaneously emitted Cherenkov photons in BGO. The OctaSiPM, developed by FBK, features a single pixel active area of 2.5 × 1.4 mm 2 and a 2 × 4 SiPM arrangement, offering a total active area of 5.3 × 5.8 mm 2 . In our recent investigation, when one end of a BGO crystal was coupled to two segmented pixels of the OctaSiPM, additional information about the initial photon density of the corresponding event could be provided. Thus, we hypothesize that the combination of the segmentation scheme and the dual-ended readout can provide multidimensional information on gamma events in BGO TOF-PET detectors. In the experimental setup, a Teflon-wrapped polished BGO crystal was read out from both ends using OctaSiPMs, followed by low-noise high-frequency amplification. Coincidence detection of gamma rays was conducted between a BGO detector and an LYSO:Ce:Mg reference detector. Relationship between segmented pixel time differences and top-bottom time differences revealed a unique pattern correlating with Cherenkov photon events. By selectively adjusting time windows, time difference distribution converged towards a single Gaussian distribution, enabling the selection of pure Cherenkov-triggered events. This marks the first instance of achieving a single Gaussian fitting from BGO data, underscoring the novelty and importance of our findings. Moreover, the analysis of initial photon counts provided insights into the likelihood of prompt Cherenkov photon detection and its temporal density.

关键词： Microwave integrated circuits Image segmentation Image resolution Fluctuations Semiconductor detectors Gamma-rays Crystals

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Continuous single-ended DOI measurement using highly (64:4) multiplexed signals

Continuous single-ended DOI measurement using highly (64:4) ...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： H. S. Shim M. J. Cho J. S. Lee Interdisciplinary Program of Bioengineering Seoul National University Seoul Republic of Korea Integrated Major in Innovative Medical Science Seoul National University Seoul Republic of Korea Department of Nuclear Medicine Seoul National University Seoul Republic of Korea

This study aims to investigate the feasibility of applying a multiplexing method that uses a high-pass filter and an artificial neural network proposed by the authors to a system. The accuracy of the proposed method was measured for four sampling rates ranging from 125MHz to 1GHz and three crystal configurations, including one-to-one coupling, light-sharing, and cDOI configuration. The accuracy was compared using the R 2 value between the true amplitude and estimated amplitude of the signal, and it was confirmed that the proposed method achieved an accuracy of 0.97 or higher in all situations. Furthermore, when measuring the DOI resolution using the cDOI configuration, the proposed method exhibited an accuracy of 0.97 or higher even under side irradiation conditions and achieved a DOI accurcacy of 74.4%. Therefore, it was confirmed that a sufficient DOI resolution could be obtained for an 8 × 8 SiPM array with a 3mm pitch attached with a 12 × 12 LSO array with a 2mm pitch using only four multiplexed readouts. This method guarantees high accuracy, sufficient multiplexing ratio, and operation at a suitable sampling rate for the system.

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Emulating Scanning Process for Stochastic Bone Scan Denoising

Emulating Scanning Process for Stochastic Bone Scan Denoisin...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： S. Bae J.S. Lee Seoul National University Interdisciplinary Program in Bioengineering Seoul Republic of Korea Seoul National University Integrated Major in Innovative Medical Science Seoul Republic of Korea Department of Nuclear Medicine Seoul National University Seoul Republic of Korea Brightonix Imaging Inc Seoul Republic of Korea

ISBN: (数字)9798350388152

ISBN: (纸本)9798350388169

Improving the quality of low-dose nuclear medicine images can reduce radiation exposure and acquisition time, and deep learning is a major trend in this area. Due to the nature of deterministic denoising, restored images are often blurred. In this study, we used the Generative Accumulation of Photons (GAP) method to stochastically denoise bone scan images by emulating the scanning process. The effectiveness of the method was evaluated using 99mTc MDP and DPD bone scan images from Seoul National University Hospital and compared with well-established deterministic denoising schemes - low-dose image to low-dose image training (Noise2Noise, N2N) and low-dose image to full-dose image supervised training (Noise2Full, N2F). The mean of stochastically sampled full-dose images using GAP showed higher structural similarity index measure (SSIM) and peak signal-to-noise ratio (PSNR) compared to N2F and N2N denoising results, along with good perceptual metrics calculated using Learned Perceptual Image Patch Similarity (LPIPS). For denoising $50 \%$ dose images, GAP achieved SSIM of 0.938, PSNR of 36.76 dB, and LPIPS of 0.039. Additionally, for denoising 20% dose images, GAP achieved SSIM of 0.891, PSNR of 34.34 dB, and LPIPS of 0.086 (average of 41 images).

关键词： Training Semiconductor device measurement Nuclear medicine Microwave integrated circuits PSNR Semiconductor detectors Noise reduction

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A Novel Energy Estimation Method for PET Detectors Composed of Multiple Scintillators

A Novel Energy Estimation Method for PET Detectors Composed ...

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IEEE Symposium on Nuclear Science (NSS/MIC)

In this study, we propose a novel technique for estimating energy in PET detectors composed of multiple scintillators. We mixed waveforms from two detectors, each containing BGO, GAGG, or LGSO scintillators, and trained a model using artificial neural networks to distinguish the energy of each waveform. We compared the accuracy of using amplitude and integration values as labels for energy estimation, using R 2 values as a metric. When applying the neural network-based energy estimator to the mixed waveforms of BGO and GAGG detectors, the R 2 values were (0.88, 0.99) for amplitude-based training and (0.95, 0.99) for integration-based training. In BGO and LGSO, the R 2 values were (0.94, 0.99) for amplitude-based training and (0.99, 0.99) for integration-based training. In GAGG and LGSO, the R 2 values were (0.99, 0.98) for amplitude-based training and (0.99, 0.98) for integration-based training. By utilizing this method, we could estimate energy in radiation detectors that combine scintillators with different properties, including phoswich detectors and meta-scintillators.

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Gamma-ray Probe Endoscope using Phoswich structure & Pulse Shape Discrimination system

Gamma-ray Probe Endoscope using Phoswich structure & Pulse S...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： M. Park H. Lee S. Song J. Hwang C. Park K. Lee J.-Y. Yeom Department of Bioengineering Korea University Seoul Republic of Korea Interdisciplinary Program in Precision Public Health Korea University Seoul Republic of Korea Global Health-Tech Research Center Korea University Seoul Republic of Korea School of Biomedical Engineering Korea University Seoul Republic of Korea

ISBN: (数字)9798350388152

ISBN: (纸本)9798350388169

This study focuses on separation of gamma-ray signals, when a high density BGO is used in place of a light guide. The purpose of utilizing BGO instead of the light guide is to shield the GAGG scintillator from background radiation while also acting as a light guide. By using a 1.5mm BGO scintillator, over 87% of side/rear gamma rays were found to interact with BGO rather than GAGG. Gamma radiation interacting with GAGG from the front and the signals interacting with BGO from the side/rear can be separated using our pulse shape discrimination (PSD) method. In addition, unlike the conventional gamma-ray PSD method that processes with raw signals, our method can separate signals processed through CSA using rising time discrimination. By shielding side/rear gamma rays, the structural/spatial limitations of detectors such as the 3 mm diameter flexible gamma probe endoscope being developed by our research team, which limits the use shielding materials, can be overcome.

关键词： Microwave integrated circuits Scintillators Shape Endoscopes Semiconductor detectors Gamma-rays Probes

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Performance Evaluation of Cs3Cu2I5 Perovskite Scintillator Grown by Seedless SEST Method

Performance Evaluation of Cs3Cu2I5 Perovskite Scintillator G...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： S. Song J. Seo M. Park J.-Y. Yeom Department of Bioengineering Korea University Seoul Republic of Korea Interdisciplinary Program in Precision Public Health Korea University Seoul Republic of Korea Department of Health and Safety Convergence Science Korea University Seoul Republic of Korea School of Biomedical Engineering Korea University Seoul Republic of Korea

ISBN: (数字)9798350388152

ISBN: (纸本)9798350388169

In this study, we utilized the seedless Slow evaporation solution growth technique (SEST) method to grow Cs 3 Cu 2 I 5 , a 0-D perovskite scintillator material, at room temperature. The growth was conducted under conditions of 23°C temperature and 40% humidity for 10 days, resulting in obtaining multiple crystals of 5 mm in size. Using single crystal Cs 3 Cu 2 I 5 detectors grown in our lab, we evaluated its performance using radioactive isotopes ${ }^{137} \mathrm{Cs},{ }^{241} \mathrm{Am},{ }^{54} \mathrm{Mn},{ }^{60} \mathrm{Co},{ }^{22} \mathrm{Na}$, and ${}^{57}\mathrm{Co}$, and acquired energy resolutions of 8.55%, 23.35%, 7.59%, 6.49%, 9.38%, and 16.8%, respectively. In comparison with polycrystalline counterparts, single crystal Cs 3 Cu 2 I 5 exhibited superior performance, although both demonstrated excellent characteristics. By comparison, measurement using GAGG:Ce as a reference scintillator with the same setup showed an energy resolution of 10.00 %.

关键词： Temperature measurement Performance evaluation Semiconductor device measurement Microwave integrated circuits Scintillators Temperature Semiconductor detectors

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Comprehensive Study on Cherenkov Radiation for Ultrafast PET Detectors, Considering Refractive Index and Wavelength

Comprehensive Study on Cherenkov Radiation for Ultrafast PET...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： H.S. Shim H. Kang J. Kim J.S. Lee Y. Jeong Interdisciplinary Program of Bioengineering Seoul National University Seoul Republic of Korea Integrated Major in Innovative Medical Science Seoul National University Seoul Republic of Korea Department of Electrical and Computer Engineering Seoul National University Seoul Republic of Korea

This study aims to investigate the characteristics of Cherenkov radiation with respect to wavelength and refractive index. Refractive index is a function of wavelength, and when it changes, not only does the gain of Cherenkov radiation increase, but also the photon loss in the medium increases. Therefore, we examine how photons of different wavelengths behave under changing refractive index conditions. We adjust the refractive index to maintain a constant emission angle of Cherenkov radiation based on the deceleration rate of electrons moving in the medium. When electrons generating Cherenkov radiation move a total of 200 μm, both long-wavelength and short-wavelength photons are emitted at the initial stage; however, only short-wavelength photons are emitted at the late stage. Although the shorter-wavelength photons arrive first among the photons that reach the detector, the longer-wavelength photons are detected more, forming a significant peak, which is due to the fact that the former experience more absorption-based photon loss in the medium than the latter.

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Optimization of Single-ended Continuous Photon Depth-of-Interaction Positioning Scheme Based on Novel Light Sharing

Optimization of Single-ended Continuous Photon Depth-of-Inte...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： H.S. Shim W. He J.S. Lee C. Levin Seoul National University Interdisciplinary Program in Bioengineering Seoul Republic of Korea Seoul National University Integrated Major in Innovative Medical Science Seoul Republic of Korea Stanford University Radiology Stanford California United States of America Seoul National University Nuclear Medicine Seoul Republic of Korea

ISBN: (数字)9798350388152

ISBN: (纸本)9798350388169

This study focuses on enhancing the DOI resolution in PET systems by optimizing a single-ended continuous DOI positioning scheme using a 2 mm pitch $12 \times 12$ LYSO crystal array with varying boundary models. Three models were evaluated for DOI resolution at different depths using SiPMs with a 3.16 mm pitch. Results showed that Model 2, which features a central fully blocked boundary, provided the best DOI resolution of $1.87 \mathrm{~mm}(\sigma)$, equivalent to a FWHM of 4.40 mm. Experiments utilized PETsys module to read the SiPM array individually, and applied row / column sum method manually. With the row / column summed data, the optimization involved comparing and refining four metrics: variance, max/sum ratio, flood map position, and the difference between sums of even and odd entries. Additionally, the coefficients between the row values and column values were optimized. These findings highlight that strategic placement of boundaries within the detector array substantially enhances DOI accuracy, making Model 2 particularly effective for precise PET imaging, and also employing a variety of metrics, rather than a single unified metric, can lead to improved depth of interaction (DOI) resolution.

关键词： Measurement Microwave integrated circuits Image resolution Semiconductor detectors Refining Crystals Arrays

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Fully Autonomous Water Monitoring by Plant-Inspired Robots

SSRN

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SSRN 2024年

作者： Jeong, Seong-Geun Kim, Jingyeong Son, Huiseong Kim, Jae Seong Kim, Ji-Hyun Kim, Byung-Gee Lee, Chang-Soo Department of Chemical Engineering and Applied Chemistry Chungnam National University Daejeon34134 Korea Republic of Bio-MAX Institute Seoul National University Seoul08826 Korea Republic of Department of Chemistry Chung-Ang University Seoul06974 Korea Republic of Interdisciplinary Program for Bioengineering Korea Republic of

Developing countries struggle with water quality management due to poor infrastructure, limited expertise, and financial constraints. The lack of consistent power further limits the adoption of modern water management facilities. Traditional water quality testing relies on periodic site visits and manual sampling by experts. This manual method is not suitable for continuous, wide-area monitoring because it cannot detect sudden contamination from heavy metal spills, and it is impractical for experts to visit multiple sites every day over a large area. To address it, we developed plant-inspired robots capable of electricity-free, low-cost, fully autonomous, water quality monitoring. Constructed from paper, the robot absorbs surrounding water through its roots. It is controlled by paper-based microfluidic logic that sends absorbed water to petal-shaped actuators only when the water is polluted. This triggers the actuators to swell and bend like a blooming flower, which visually signals the presence of pollutants to local residents. The paper robot can be mass-produced at low cost and deployed over larger area. Once installed, it can autonomously operate using only water as fuel, thereby eliminating the need for electricity or expert intervention. This autonomous robot offers a new approach to water quality monitoring suitable for resource-limited environments. © 2024, The Authors. All rights reserved.

关键词： Heavy metals

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Statistically-based inter-crystal scatter event positioning method for a 3D position sensitive TOF detector based on side readout

Statistically-based inter-crystal scatter event positioning ...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： H.S. Shim Z. Zhao J.S. Lee C. Levin Seoul National University Interdisciplinary Program in Bioengineering Seoul Republic of Korea Integrated Major in Innovative Medical Science Seoul National University Seoul Republic of Korea Stanford University Radiology Stanford California United States of America Seoul National University Nuclear Medicine Seoul Republic of Korea

ISBN: (数字)9798350388152

ISBN: (纸本)9798350388169

This study investigates a statistically-based method for positioning inter-crystal scatter (ICS) events in a 3D position-sensitive TOF detector using a side readout scheme. The experimental setup utilized a side readout with a 130 ps coincidence time resolution (CTR) and an energy resolution of less than 10%. Various methods were explored to accurately position ICS events, primarily using energy information and crystal identification via multiplexed signals. ICS events were defined as having two crystal identification signals per event, whereas photoelectric events only had one. The results showed that assigning the first interaction position using the maximum energy deposited method yielded an accuracy of 54.98%, while the minimum energy method resulted in 45.02% accuracy. We also introduced the proportional ICS positioning method to this side readout which utilize the ratio between the photoelectric event and the ICS event. The proportional ICS positioning method demonstrated high consistency, with $\mathrm{R}^{2}$ values above 0.97, indicating a strong predictive ability for the number of ICS events based on the number of photoelectric events. This method suggests an effective approach to maintaining sensitivity and accurate line-of-response assignment in PET systems. The findings are pivotal for enhancing the accuracy and reliability of PET imaging, with future research aimed at applying these methods to multi-layer block configurations to address ICS occurring between layers.

关键词： Temperature sensors Temperature distribution Accuracy Three-dimensional displays Sensitivity Semiconductor detectors Energy resolution

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